794 ME. B. BETCE ON THE [Juno 15, 



of cold, when the moss is frost-bound, are rarely of long duration. 

 In the far north latitude of Spitsbergen, circa 78°, the frozen 

 state is the rule, the moist the brief exception, and an individual 

 Callidina (whose average existence may be reckoned as comprising 

 at least some three months of active life) may quite possibly live 

 during several summers, expending its three months in annual 

 instalments. This capacity for the endurance of long periods of 

 cold was already known from Ehrenberg's (4) discovery of certain 

 forms on the Swiss Alps at a great elevation. The few species 

 noted by him all belong to the Bdelloida, so that whilst the 

 present list widens the record as regards that group, it extends it 

 to at least 7 species of the PloVma. 



There appear to be but two previous records of Rotifera at so 

 high a latitude. 



In 1862 A. von Goes recorded two species of Callidina, which 

 he had found in some moss ; the species were not, however, deter- 

 mined (" Om Tardigrader, Anguilluhe m.m. fran Spetsbergen," 

 Ofvers. K. Vet.-Akad. Forh. 1862, p. 18). 



In 1869 Ehrenberg (5) had brought to him some matei-ial which 

 had been collected in Spitsbergen in 1867. This material included 

 some mosses, and in these he found one Eotifer, Callidhia alpium, 

 and an "egg of a Eotifer " unknown, among several forms belong- 

 ing to other orders. This statement occurs in a Eeport upon the 

 results aiforded by material collected by the Second German 

 North Polar Expedition of 1869 and 1870". 



Eor the rather lower latitudes of Greenland, several lists have 

 already been published, the most important being contained in the 

 treatise by Bergendal (1), in which are enumerated and discussed 

 some 82 species collected by the author at a arious localities be- 

 tween the parallels of 66° and 70° N. during the summer of 1890. 

 At first sight it appears curious that, with but three exceptions, 

 none of the forms found by hiui in Greenland have occurred in 

 the Spitsbergen material. Bergendal, however, devoted his atten- 

 tion chiefly to the ordinary water-dwelling Eotifera, and seems to 

 have rarely examined mosses. Nor does he seem to have been 

 cognisant of the fact that moss-dwelling Eotifera can be secured 

 and studied at leisure months after collection, as was done by 

 Ehrenberg and as has been done in the present case. There is 

 therefore no real ground for comparison between his list and that 

 hereto appended. It may be mentioned that, of the eleven species 

 of the Bdelloida included by him, one only has been found in the 

 course of this investigation. 



Notwithstanding their Arctic nativity, many of the species were 

 kept alive for weeks in small cells, whilst others seem at this date 

 (April 1897) to have permanently established themselves in a jar 

 of water, into which I have from time to time thrown moss which 

 I had washed, as well as washings after final examination. 



The majority of the species have already been sufficiently 

 described, and in these cases I have merely indicated their com^ 

 parative abundance in the five tins which yielded positive x-esults. 



